Preparation and Characterization of Protein Isolate from Cowpea (Vigna unguiculata L. Walp.)

ABSTRACT: Protein isolate (PI) was prepared from 3 cowpea varieties and 2 soybean varieties in each of 2 y. The protein contents of cowpea PI (CPI) (91.4% to 91.8%) and soy PI (SPI) (93.0% to 93.5%) were significantly different ( P < 0.05). Electrophoretogram showed that CPI was concentrated at 60 and 40 kDa, whereas SPI showed bands at 95, 65, 60, 40, and 35 kDa. The CPI had higher lysine (49.3 to 51.8 mg/g) than SPI (41.9 to 43.4 mg/g). The CPI and SPI had surface hydrophobicities ranging from 387.8 to 572.9 and 640.6 to 643.1, respectively. Denaturation temperature (85.2 to 88.4 °C) and enthalpy (8.42 to 10.33 J/g) of CPI were similar to the 7S fraction of SPI (82.6 °C and 96.0 to 96.3 J/g). These characteristics of CPI might be useful to explain its functionalities for application in food systems.     

Functional Properties of Protein Isolate from Cowpea (Vigna unguiculata L. Walp.)

ABSTRACT: Functional properties of protein isolates prepared from 3 cowpea varieties and 2 soybean varieties in each of 2 y were determined. Both cowpea protein isolate (CPI) and soy protein isolate (SPI) showed a u-shaped curve for solubility with the minimum solubility occurring at pH 4.5. The CPI had lower emulsifying activity than SPI but was similar in stability. Foaming capacity and foaming stability ranged from 58.6 to 60.2 mL and 63.7 to 64.4 min for CPI and from 31.9 to 33.0 mL and 43.4 to 45.0 min for SPI, respectively. Gels were formed at 70 °C for 40 min and 30 min for CPI (12%) and SPI (10%), respectively. The CPI needs modification to enhance functional properties for potential application in food products.     

Evaluation of cooking time and quality of seven diverse cowpea (Vigna unguiculata (L.) Walp.) varieties

Seven cowpea ( Vigna unguiculata (L.) Walp.) varieties, which were part of a larger collection evaluated in agronomic field trials in Botswana, were selected for characterization of cooking time and quality. Newly harvested seed was kept in the open air for 2 weeks, then stored at 4°C and 40% relative humidity for 3 months. Duplicate samples were tested for cooking time with and without 12-h prior soaking. Varieties showed differences ( P < 0.01) in cooking time and response to soaking, although the overall effect of soaking was insignificant. Cooking times ranged from 29 to 64 min without soaking and 36 to 56 min after soaking, with small-seeded varieties having the longer cooking times. The seed coat of some varieties readily became soft, but others remained tough or split before finally softening.     

Mineral Loss in Cowpeas [Vigna unguiculata (L.) Walp] by Pressure Heating in Water

White Acre cowpeas of four maturity levels were heated in water at 35 kPa for 0–40 min. As the cowpeas increased in maturity, Zn, Cu, Mn, Mg, and K increased, Fe decreased and Ca did not change. All minerals analyzed decreased with heating: Cu, Ca and Mg (p < 0.001), Zn, Fe and K (p <0.01) and Mn (P<0.05). Minerals leached from the cowpeas at different magnitudes and rates. For example, K lowered 70–80% within 10 min; others lowered 20% or less. Loss of minerals across maturity stages was not uniform. This method reduced loss of certain minerals when compared to published values for the boiling water method.     

紫皮豇豆(Vigna unguiculata L.)花色苷的研究

首次应用高效液相色谱-二极管阵列检测器-质谱联用技术(HPLC-DAD-MS)鉴定出紫皮豇豆主要含有三种花色苷,分别为飞燕草色素、矢车菊色素、天竺葵色素的葡萄糖苷,其中矢车菊葡萄糖苷相对百分含量达到93.4%;应用pH示差法测定出其单体花色苷的含量为57.15mg/100g鲜重;应用DPPH法测定结果显示,花色苷粗提液有较强的抗氧化能力。     

Anthocyanins in cowpea [Vigna unguiculata (L.) Walp. ssp. unguiculata]

The aim of this study was to isolate and identify the anthocyanins in the black seed coated cowpea [Vigna unguiculata (L.) Walp. ssp. unguiculata] using reverse phase C-18 open column chromatography and high performance liquid chromatography (HPLC) with diode array detection and electro spray ionization/mass spectrometry (DAD-ESI/MS) analysis, respectively. Anthocyanins were extracted from the coat of black cowpea with 1% trifluoroacetic acid (TFA) in methanol, isolated by RP-C-18 column chromatography, and their structures elucidated by 1D and 2D nuclear magnetic resonance (NMR) spectroscopy. The isolated anthocyanins were characterized as delphinidin-3-O-glucoside (2) and cyanidin-3-O-glucoside (4). Furthermore, 5 minor anthocyanins were detected and identified as delphinidin-3-O-galactoside (1), cyanidin-3-O-galactoside (3), petunidin-3-O-glucoside (5), peonidin-3-O-glucoside (7), and malvidin-3-O-glucoside (8) based on the fragmentation patterns of HPLC-DADESI/MS analysis.     

Genetics of bruchid (Callosobruchus maculatus Fab.) resistance in cowpea (Vigna unguiculata (L.) Walp.)

Bruchid resistance has been measured using a variety of techniques. Mean development period (MDP) and percentage adult emergence (PAE) are two of the more important traits measuring bruchid (Callosobruchus maculatus Fab.) resistance in cowpea. The objective of the study was to evaluate the genetic relationship between MDP and PAE in C. maculatus resistant cowpea. Seventy-two F₂ population plants were developed from the cross between C. maculatus resistant TVu-11953 (with delayed MDP and low PAE) and C. maculatus susceptible Ife Brown (with early MDP and high PAE) which were evaluated for resistance to cowpea C. maculatus. MDP at 45 days after infestation (DAI) and PAE at 60 DAI were taken as analysed measures for resistance to C. maculatus infestation. Data generated were subjected to chi-square analysis. Varied resistant response to C. maculatus infestation was observed among the F₂ generation plants but their responses showed inclination to the susceptible parent. A 15:1 ratio for susceptible to resistant genotypes was observed with MDP among the F₂ genotypes evaluated which is an indication of the presence of two recessive genes that control of MDP. The segregation of PAE also showed a 15:1 ratio goodness of fit (P > 0.05) for susceptible to resistant genotypes. Test of independence between MDP and PAE was not significant (χ² = 2.19, P = 0.19). This study revealed that the recessive genes controlling these two traits (MDP and PAE) were independently assorted and showed no linkage. This was also evident in the observed F₂ genotypes with C. maculatus resistance expressing either delayed MDP or low PAE and not both in the study.     

Influence of cowpea (Vigna unguiculata L Walp) variety on protein quality and sensory properties of akara,a popular West African cowpea‐based food

The influence of newly developed cowpea varieties (IT81D‐699, IT82E‐18, IT84S‐2246‐4 and TV_x3236) on the proximate composition, protein quality and sensory properties of akara, a popular West African cowpea‐based food, was investigated and the results obtained were compared with those for akara prepared from a local blackeye cowpea variety. Protein quality was evaluated using weanling albino rats fed diets which were formulated to supply 10% protein using defatted akara samples, with casein as a control. Akara samples prepared from IT81D‐699 and TV_x3236 had crude protein contents, texture and overall acceptability comparable to those of akara prepared from the blackeye variety. Also, akara diets formulated using IT81D‐699 and TV_x3236 showed significantly (p < 0.05) higher values for weight gain, protein efficiency ratio, net protein ratio and true digestibility than diets formulated with IT82E‐18, IT84S‐2246‐4 and blackeye, suggesting an improvement in the nutritional quality of akara produced using these (IT8ID‐699 and TV_x3236) newly developed cowpea varieties. Copyright © 2004 Society of Chemical Industry     

Stability of protein digestibility and composition of cowpea (Vigna unguiculata L. Walp.) during sealed storage at different temperatures

Whole grains and flours of two cultivars of cowpea ( Vigna unguiculata ) were stored sealed at steady temperatures of 0, 20 and 55°C, and 11–13% moisture for 7 months. The pH, soluble sugars, free amino nitrogen, titratable acidity, and protein digestibility decreased at 55°C. The changes varied with cultivar and between the flours and the grains stored at 0 and 20°C. All changes, except titratable acidity in white cowpea flour, were strongly correlated with increasing storage temperature.     

In vitro and in vivo digestibility of the albumin and globulin fractions of eight Brazilian cowpea [Vigna unguiculata (L) Walp] cultivars

Cowpea (Vigna unguiculata) is a very important crop for people living in the north‐east of Brazil where it constitutes the principal source of protein and carbohydrate. In this study, it was observed that the in vitro digestibility of the seed albumin and globulin fractions extracted from eight Brazilian cowpea cultivars was high when treated with pepsin but resistant to degradation by trypsin or chymotrypsin even after 3 h of treatment. When the albumin and globulin fractions were given to rats by intragastric intubation it was observed that intact proteins or their fragments were immunodetected in the faeces. Immunohistochemical analyses of the gut sections of these rats showed that a proportion of the albumin fraction (or its fragments), but not the globulin one, was bound to the brush border enterocytes in the duodenum. Thus the incomplete enzymatic degradation of both globulin and albumin fractions as well as the albumin binding to the gut may have a bearing upon the growth depression, malabsorption and diarrhoea observed on rats fed on cowpea seeds. Copyright © 2004 Society of Chemical Industry     

Hydrothermal treatments of two cowpea (Vigna unguiculata L. Walp) varieties: effect of micronisation on physicochemical and structural characteristics

The effects of a hydrothermal treatment consisting of tempering (to 41% moisture) and heating to 153 °C (micronisation) on the structural and physicochemical characteristics of two cowpea varieties were studied. The untreated varieties had similar cooking times, although cooked Bechuana white cowpeas were significantly (P ≤ 0.05) softer and had a higher incidence of splitting than Var. 462 cowpeas. This may be due in part to differences in cotyledon structure affecting water uptake during cooking. The hydrothermal treatment changed the physical structure and chemical properties of the cowpea seeds. This led to significant (P ≤ 0.05) reductions in the cooking time of micronised Bechuana white and Var. 462 cowpeas, by 47 and 36% respectively, as compared with control samples. Micronisation caused physical fissuring of the seed coat and cotyledon and significantly (P ≤ 0.05) reduced the bulk density of treated seeds. These changes in the physical structure significantly (P ≤ 0.05) improved the initial water uptake during soaking and cooking, increased the enzyme‐susceptible starch and reduced the protein solubility and hydration capacity of the cowpea seeds. Cooked (60 min) micronised cowpeas also had significantly (P ≤ 0.05) more splits and a significantly (P ≤ 0.05) softer texture than control samples. Copyright © 2005 Society of Chemical Industry     

Gamma irradiation of cowpea (Vigna unguiculata L. Walp) seeds: effect on colour,cooking quality and pasting characteristics

Cowpea seeds were treated to various gamma irradiation doses, and their colour, cooking quality and pasting properties studied. Irradiation at 50 kGy resulted in significant browning (indicated by decreases in L colour value) of cowpea seeds. At 2 and 10 (but not at 50) kGy, irradiation led to significant reduction in cooking time of cowpea seeds possibly through irradiation‐induced degradation of starch and pectic substances (indicated by decreases in peak and final viscosities) leading possibly to enhanced heat and mass transfer within the seed cotyledon and cell wall, respectively. At 50 kGy, the cooking time of cowpea seeds was prolonged significantly owing possibly to extensive polymer cross‐linking occurring within the seeds at this high dose. Splitting of cowpea cotyledons during cooking decreased significantly at 50 kGy, but was unaffected at 2 and 10 kGy. Irradiation resulted in significant leaching of nutrients from cowpea seeds during cooking in a dose‐dependent manner.     

Physico-chemical properties of the flours and starches of two cowpea varieties (Vigna unguiculata (L.) Walp)

The physical and chemical properties of the starches and flours of whole grain and decorticated two cowpea varieties (Vigna unguiculata (L.) Walp) were investigated. The two cowpea varieties were: C-152-White, having big grain and S-1552-White, having small grain with black eye. Results showed that starch yields were 19.2 and 16.4 g/100 g grain for C-152 and S-1552, respectively. Statistical analysis shows that the total amylose contents of the starch of the two cowpea varieties were significantly higher (P ≤ 0.05) than that of the whole grain and decorticated flours. The swelling power of C-152 starch was significantly higher than that of S-1552 starch. The water-binding capacity (WBC) for S-1552 starch was higher than for C-152 starch. The results of pasting profile of both the flour and the starch showed that the two cowpea varieties possess different properties in relation to gelatinization temperature(GT), peak viscosity (PV), hot paste viscosity (HPV), cold paste viscosity (CPV), break down (BD), set back (SB), total set back (SBt) and relative breakdown (BDr). The information generated in this study on the properties of the starch could provide guidance on possible industrial uses of starches of these two varieties.Industrial relevanceThis work showed the peculiar characteristics (solubility, water-binding capacity, amylose content, carbohydrate composition, granules characteristics and behaviour in Brabender viscoamlograph) of pure cowpea starch. The results that we obtained could be very valuable in decision making for industries that want to take advantage of cowpea starch as alternative or supplement to cereal/tuber starch. Cowpea starch could be useful in the manufacture of thickeners, gelling agent, extenders and texture modifiers in food formulation.     

Genetic and environmental variability in starch,fatty acids and mineral nutrients composition in cowpea (Vigna unguiculata (L) Walp)

Fifteen cowpea cultivars grown in three locations (Kano (12°00′N 8°31′E), Mokwa (9°17′N 5°04′E) and Ago-Iwoye (6°58′N 4°00′)) between 1993 and 1994 were analysed for genotype, environmental and genotype×environment variability for starch (g kg⁻¹), fatty acids (% of total oil) and mineral nutrients (g kg⁻¹) composition. There were significant environmental as well as genetic effects on these nutritional qualities. The environmental effect accounted largely for the variability observed in starch (60%), palmitic acid (80%), arachidic acid (100%), potassium (100%), phosphorus (81%) and manganese (86%), while the genotypic effect accounted largely for the variability observed in linoleic acid (50%), linolenic acid (50%) and copper (68%) contents. Correlation coefficient (pooled data) from the three locations indicated that starch was positively correlated to palmitic acid (r = 0·21, 0·01< P < 0·05), potassium (r = 0·80, P < 0·001) and phosphorus (r = 0·65, P < 0·001), but negatively correlated to oleic (r = −0·23, 0·01< P < 0·05), linoleic (r = −0·67, P < 0·001) and linolenic acid (r = −0·74, P < 0·001) contents. Starch showed a strong positive correlation with magnesium content (r = 0·75) and a strong negative correlation with copper (r = −0·73) and iron (r = −0·62) at the genetic level. This research established the degree of variability for these characters in cowpea. © 1998 Society of Chemical Industry.     

Imitation milks from Cicer arietinum (L.), Vigna unguiculata (L.) walpers and Vigna radiata (L.) wilczek and other legumes

Vegetable milks were prepared in the laboratory from mung bean [Vigna radiata (L.) Wilczek], cowpea [Vigna unguiculata (L.) Walpers] and chick-pea [Cicer arietinum (L.)] by homogenisation of a filtered aqueous extract of the ground legume with soya bean oil. Emulsions stable to pasteurisation were made from the first two. Pigeon pea [Cajanus cajan (L.)] and black gram [Vigna mungo (L.) Hepper)] were found to be unsuitable as bases for milks prepared by simple processing. The nitrogen, oil, sugar and ash contents of the first three legumes, and of milks prepared from them, were determined. Imitation milks are intended to resemble animal milks nutritionally, and whilst the contents of potassium and phosphorus were acceptable, these vegetable milks were low in sodium, calcium and zinc. The trypsin inhibitory activity, whilst low in comparison with soya milk, was partially stable to pasteurisation. The amino acid composition indicated that it would be desirable to complement legume proteins with cereal proteins to prepare vegetable milks.     

Cowpea (Vigna unguiculata L. Walp), a renewed multipurpose crop for a more sustainable agri‐food system: nutritional advantages and constraints

The growing awareness of the relevance of food composition for human health has increased the interest of the inclusion of high proportions of fruits and vegetables in diets. To reach the objective of more balanced diets, an increased consumption of legumes, which constitutes a sustainable source of essential nutrients, particularly low‐cost protein, is of special relevance. However, the consumption of legumes also entails some constraints that need to be addressed to avoid a deleterious impact on consumers' wellbeing and health. The value of legumes as a source of nutrients depends on a plethora of factors, including genetic characteristics, agro‐climatic conditions, and postharvest management that modulate the dietary effect of edible seeds and vegetative material. Thus, more comprehensive information regarding composition, especially their nutritional and anti‐nutritional compounds, digestibility, and alternative processing procedures is essential. These were the challenges to write this review, which focusses on the nutritional and anti‐nutritional composition of Vigna unguiculata L. Walp, an emerging crop all over the world intended to provide a rational support for the development of valuable foods and feeds of increased commercial value. © 2016 Society of Chemical Industry     

Composition and bioactive factor content of cowpea (Vigna unguiculata L. Walp) raw meal and protein concentrate

Analysis was done of the composition and bioactive factor content of whole meal, processed meal and protein concentrate from a cowpea cultivar (Vigna unguiculata L. Walp var. IT86D‐719) grown in Yucatan, Mexico and of changes in these parameters after soaking and dehulling. Both meals had a high protein content (247.53 and 257 g kg^?1 dry matter (DM) respectively). The protein concentrate was rich in protein (786 g kg^?1 DM) and lipids (58.47 g kg^?1 DM) and had an amino acid profile similar to that of the processed meal. The amino acid profiles of the meals almost covered human dietary requirements based on FAO/WHO/UNU‐suggested profiles but were deficient in sulphur amino acids. Trypsin inhibitor activity was high in both meals compared with levels found in previous studies. Trypsin inhibitor activity in the concentrate was not eliminated but was significantly reduced. Lectin activity, tannin levels, phytate levels and α‐amylase inhibitor activity were relatively low in the meals, and cyanogenic glucosides were not detected. Residual amounts of α‐amylase inhibitors, tannins and phytate were observed in the concentrate, and lectin activity was not detected. Results indicate that V. unguiculata L. Walp var. IT86D‐719 meals and protein concentrate are good potential foodstuffs in the Yucatan region. Copyright © 2006 Society of Chemical Industry     

Prebiotic effect of resistant starch from Vigna unguiculata (L.) Walp. (cowpea) using an in vitro simulated digestion model

There has been growing interest in the use of resistant starch (RS) as a prebiotic for physiological benefits and to reduce the risk of chronic diseases. In this study, RS was isolated from samples of five cowpea cultivars (DT129-4, TVU 11424, PAN 311, Fahari and Bechuana White) seeds to determine their potential prebiotic effects, and proximate and mineral composition. Results obtained showed samples of five cowpea cultivars to be high in protein (18.0–28.7%) and carbohydrates (54.9–66.0%) and low in fat (0.6–3.7%). The RS from cowpea samples ranged between 9.3 and 12.1% with cultivar DT129-4 having the highest amount. Fermentation of RS using mixed and pure cultures was done, and bacterial growth was monitored over a 24-h period. Resistant starch isolated from all cowpea samples fulfilled the criteria to be classified as a prebiotic which have a wide range of beneficial effects on the host, with cultivar DT129-4 showing the most prebiotic potential amongst cowpea samples tested.